The consumer desire for dryer sheets capable of providing fabric conditioning benefits during the drying process is known. Conventional dryer sheets are typically made up of non-woven fibrous substrates which are impregnated with fabric conditioner actives such as cationic softening agents, antistatic agents, dispersing agents and fragrance agents. Typical non-woven fibrous substrates are made of polyester. The fabric conditioner is applied to the non-woven fibrous substrate and then dried in an oven so that the dryer sheet is “dry” when ready for use. The fabric conditioners impregnated on the dryer sheet are then released in the course of the drying cycle. Examples of conventional dryer sheets are reported in U.S. Pat. Nos. 3,939,538 to Marshall et al.; 4,118,525 to Jones et al.; 5,066,413 to Kellett; and 6,254,932 to Smith et al.
One problems encountered with conventional dryer sheets using non-woven substrates is that the non-woven substrate are limited in their ability to load fabric conditioner. Fabric conditioner compositions are typically loaded onto conventional dryer sheets by releasably affixing the fabric conditioner composition into the interstitial spaces of the non-woven fibers. The ability of the non-woven substrates to accommodate varying levels of fabric conditioner loading is thus a function of the fiber dimensions and the bonding techniques used to form the non-woven substrate. There remains a continual need for alternative types of substrates which can accommodate larger ranges of fabric conditioner loading levels.
Another problem encountered with conventional dryer sheets is that they tend to retain unacceptable amounts of residual fabric conditioner after being used in one complete automatic drying cycle in an automatic drying cycle. It is believed that as much as 20%, up to 33%, or even up to one half, of the fabric conditioner actives can remain on a dryer sheet after a complete drying cycle. This phenomenon causes some consumers to believe that the residual fabric conditioner present on the used dryer sheets can still be used for additional loads. The problem is that the re-use of sheets designed for single use delivers less fabric conditioning benefit causing consumers to receive inconsistent results when using dryer sheets.
Additional problems with conventional dryer sheets are that the “dried on” fabric conditioners have been reported to exhibit limited softening capability yet require more energy (heat) for proper use when compared to liquid fabric softeners. Recent attempts to address the problems with dry dryer sheets disclose the use of non-woven dryer sheets for delivery of liquid fabric conditioner actives. These problems and examples of attempts to address these problems are reported in U.S. Patent Publ. Nos. 2007/0015676 and 2007/0256273 both to Ogden et al.
Despite the many attempts to address the problems with conventional dryer sheets, these attempts have focused on the use of fibrous substrates or sponge/foam materials. There remains a need for a fabric conditioner sheet which is capable of increased fabric conditioner loading levels yet provides suitable fabric conditioner release rates. Further, there is a need to provide fabric conditioner sheets which can accommodate both liquid and dried fabric conditioners